1) Characterize the pre-obese state with regard to energy expenditure, phys al activity and body composition, 2) Identify environmental and phenotype mar rs for the development of human obesity, 3) Examine the effects of increasing e level of physical activity in pre-obese children on energy expenditure and e subsequent development of obesity and 4) Derive estimate of energy requirem ts in children based on measurements of energy expenditure, rather than on ene y intake data.